<?php
$_fp = fopen("php://stdin", "r");
/* Enter your code here. Read input from STDIN. Print output to STDOUT */

fscanf($_fp, "%d", $n);
for($i = 0; $i < $n; $i++){
    fscanf($_fp, "%d", $pts);
    $highX = 0;
    $highY = 0;
    $result = "YES";
    for($j = 0; $j < $pts; $j++){
        fscanf($_fp, "%d %d", $xpt, $ypt);
        if($xpt > $highX){
            $highX = $xpt;
            if($ypt > $highY){
                $result = "NO";
                break;
            }
        }
        if($ypt > $highY){
            $highY = $ypt;
            if($xpt > $highX){
                $result = "NO";
                break;
            }
        }
        if(($xpt != 0 && $xpt != $highX ) || ($ypt != 0 && $ypt != $highY)){
            $result = "NO";
            break;
        }
    }
    echo $result . "\n";
}

?>